Download DNA

Objective and Catalyst
Students will:
•  Explain the process and importance of DNA replication
and base-pairing
•  Model DNA replication using paper clips
In order to explain how a genetic trait is determined by the code in a
DNA molecule
Catalyst
1.  DNA is an example of __________ (macromolecule)
2.  The building blocks of DNA are ____________.
3.  These building blocks are made of 3 parts:
_____________, _________, and ________.
DNA
Yeah, you know what it is
At least you should….
DNA
•  DNA stands for deoxyribonucleic
acid
•  It is a nucleic acid made of
nucleotides
– Each nucleotide is made of 3
parts
• Sugar
• Phosphate
• Nitrogen Base
DNA
•  Nitrogen Bases – 4 Bases in DNA
–  Adenine
–  Thymine
–  Guanine
–  Cytosine
DNA
DNA is in the shape of a helix
–  This is similar to a spiral staircase or
twisted ladder
•  Since DNA is 2 strands, it is considered
a DOUBLE HELIX
DNA
•  The nitrogen bases make up the
“rungs” of the DNA double helix.
•  Each base pairs-up with another base
in order to connect the 2 strands of
DNA
•  The bases will ONLY pair with one
other base:
• 
A-T and T-A
• 
C-G and G-C
DNA- Chargraff’s Rule:
Erwin Chargraff studied DNA and
found that the amount of adenine =
the amount of thymine.
He also noted that the same was
true for cytosine and guanine
This discovery is the reason we
understand the structure of DNA
and the pairing of the bases!
The idea that these bases always
pair in the same way allows for
DNA replication to be extremely
accurate. WHY?
DNA
•  DNA replicates during what important
cellular process?
•  What are the 3 main reasons that cells
undergo this process?
Let’s Replicate some DNA
•  Here is the original strand of DNA:
complete the other strand using your base
pairs rule
•  A T G C C C G T T A T C G A
DNA
•  Now in order to replicate, the strands split
apart
•  The new strands created are called
complementary strands
Here our original strand has split into
two single strands
•  A T G C C C G T T A T C G A
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•  T A C G G G C A A T A G C T
•  Make the complimentary strands for the two original
strands of DNA
•  Are the two newly replicated
strands of DNA identical? •  How does the rule of base pairs
make this possible? Importance of DNA Replication
•  What is the purpose of DNA?
–  It is the “instruction book” for our cells!
–  Remember PB&J?
•  What would happen if your cells had
different instructions?
•  When does DNA replication happen?
•  Why is it important that DNA replication go
well?
•  What would happen if the bases did not
copy properly?
DNA Modeling (Paper Clip)
•  Learning Target: DNA Structure & Replication
•  I Can… Create a simulated gene segment of DNA
and take the segment through the process of
replication.
•  I Will…
•  Create a simulated primary segment of a gene
representing the nucleotide types within the
sequence with assigned colored paperclips.
•  Predict and create a complementary strand of DNA
using the base pairing rules.
•  Unzip and replicate the DNA gene segment
explaining the steps of the process.
Quick Review:
• Each DNA molecule has a unique structure that
makes it different from other
DNA molecules (Remember – A chromosome is
condensed DNA and segments of DNA are
genes.)
• This difference occurs because the sequence of
A, T, C, and G vary from one molecule and gene
segment to another.
What You Need to Know About
DNA Replication:
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To “replicate” DNA means to produce an exact copy of itself. DNA
is the only known molecule that can do this regularly – RNA has
been known to replicate under laboratory conditions,
DNA is able to make an exact replica of itself because of the base
pairing characteristics stressed earlier (A with T and C with G).
When DNA makes a duplicate molecule of itself, the two strands
unwind.
After the two strands have pulled apart, new bases (A, T, C, & G) as
well as new sugar and phosphate units come into place according to
the base pairing rules.
A comes in opposite of T, and C is opposite of G.
When this occurs, two identical DNA molecules are created.
DNA Modeling
•  Read outloud and follow the steps.
•  Work together!
•  Mrs. Reigel will come around to check
your progress
•  When you finish, answer the conclusion
questions.
Exit Slip
1.  What two molecules are found on the
“sides” of the DNA ladder?
2.  What makes up the “rungs” or “steps” of
the ladder?
-Fill in your HW section
-Circle how well you understood the lesson
today
-Turn in: Green WWO, DNA Lab
-Take home: DNA Practice (HW) and notes
Clean Up
-Put your paper clips back in the envelope
**No Exit Slip**
-Fill in your HW section
-Circle how well you understood the lesson
today
-Turn in: Green WWO, DNA Lab
-Take home: DNA Practice (HW) and notes